The present invention relates to signal isolators and, particularly, signal isolators that operate according to an on-off keyed signal protocol.
Isolators are devices that exchange data signals between two galvanically isolated circuit systems. The circuit systems each operate in different voltage domains, which may include different source potentials and different grounds. Isolation devices may provide data exchange across an isolation barrier, which maintains the galvanic isolation. Typical isolation devices include micro-transformers, capacitors, magneto-resistors/giant magneto-resistors and opto-electronic devices.
On-off keying (“OOK”) is a signaling protocol that identifies a digital state based on the type of signal that is transmitted through the isolation barrier. A first digital data state (say, a digital “1”) might be signaled by transmitting a periodic signal across the isolation barrier. A second digital data state (a digital “0”) might be signaled by transmitting no signal across the isolation barrier. A receiver circuit would detect the presence or absence of the periodic signal and decode a digital output signal therefrom.
OOK-based signal isolators typically have inefficient designs. For example, isolator transmitters may include a high-frequency oscillator separate from the isolator device to generate a carrier that becomes the periodic signal. Moreover, transmitters often are power-hungry devices. Accordingly, the inventors perceive a need in the art for an improved transmitter architecture for OOK-based signal isolators.